Mufflers for internal combustion engines may employ packing materials to attenuate noise exiting the exhaust system. These materials tend to comprise short fibers that are mechanically pressed into blankets or blown into a cavity. The problem is that the short fibers tend to break free in service and are expelled from the muffler. This significantly reduces the amount of fibers left in the muffler and thus reduces the noise attenuation properties of the muffler.
U.S. Pat. No. 6,978,643 to Akers et al. discloses multilayer sleeves for insulation for protecting elongated substrates. This structure is not disclosed as being useful as a muffler packing for internal combustion engine mufflers. The sleeves are continuously knitted in different sections integrally joined end to end, the sections being formed of different filamentary members chosen for desired characteristics. The sleeves are formed into the multilayer configuration by reverse folding the sleeves inwardly to place one section concentric within another. The sleeve ends may be finished with welts to prevent raveling and serve as a clinch on the elongated substrates. Rib knits are used to form insulating air pockets lengthwise along the sleeves to augment the insulating effectiveness.
The sleeve comprises a first flexible tubular segment formed from interlaced base filamentary members such as metal wire and fiber filaments by knitting. A second flexible tubular segment is formed of interlaced filamentary members also of base wire filaments interlaced with fibers. The inner segment is formed from glass, quartz or other mineral fibers that are resistant to high temperatures.
The first and second segments are each folded circumferentially inward to form the first and second segments each into two coaxial segments. The outer segment is formed of DREF fiber yarns and glass fibers are used to form the inner segment to permit manual handling of the outer segment without harshness as exhibited by glass fibers. The interlaced filaments have different characteristics. The base filamentary members of each segment may be wires and the interlaced filamentary members of each segment are fibers. This structure requires all of the segments to comprise a base wire filament knitted with a second fiber filament and also requires the fibers of the outer segments to be DREF and the inner segments to be glass fibers for handling purposes.
This construction is relatively complex and costly in that both wires and fibers are required throughout the various outer and inner segments. Also it requires additional costly folding steps to reversely fold the various segments to form coaxial related segments.
U.S. Pat. No. 4,278,717 to Aoyama is not disclosed as useful as a packing for use with internal combustion engine mufflers and discloses a heat resistant cushion in the form of a compact toroidal structure which is formed by an annular network of knitted metal wires. The network includes a first segment which forms an outer surface of the toroidal structure and a second inner segment containing yarns of an inorganic fiber which disposed at a given axial separation and extend circumferentially of the network. The fibers are supported by engagement with selected loops of metal wires, such as every third course of knitted wires, which forms the second segment. The network structure is rolled upon itself beginning with the free end of the second segment to form a toroidal structure.
U.S. Pat. No. 3,949,828 to Frochaux discloses a fluid exhaust silencer comprising a hollow cylindrical fluid permeable noise-reducing element made of wire mesh. The noise reducing element is mounted in a housing which is adapted to be connected to an exhaust for a pressurized fluid. The housing is made so that the pressurized fluid flows into one end of the housing and is discharged from the side of the housing after passage through the noise reducing element. However, this structure is not disclosed as useful with present internal combustion engine exhaust mufflers.
U.S. Pat. No. 5,799,395 to Nording et al. discloses a process for manufacturing an air gap insulated exhaust pipe. An air gap insulated exhaust pipe has a sliding fit between two inner pipe sections in a middle area of the length of the exhaust pipe and has a radial mounting to the inner pipe in the outer pipe which is provided in the area of a bend or beyond the bend, which joins the leg of the exhaust pipe in which the sliding fit is located. This structure is not disclosed as useful for correcting an internal combustion engine muffler loose packing problem discussed above.
The present inventors recognize a need for a solution to the above problem with present muffler packings. In particular, they recognize a need for a sleeve for sound/heat insulation for tubular members especially one that can be for used as a packing for exhaust mufflers of internal combustion engines to preclude loss of the fibers as presently occurs or for use with other high temperature or noisy tubular members or applications and is low cost to fabricate and easily manufactured. The prior art systems described above are believed to be costly to make or believed to not adequately serve as muffler packing for internal combustion engine exhaust systems by way of example.